Extracellular calcium ion concentration is involved in a variety of biological processes, such as blood clotting, nerve and muscle excitability and bone formation (Cell Calcium 11:319, 1990). One of the key elements of this regulation is the calcium receptor known as the Ca sensing receptor (CaSR). Calcium ion receptors, which are present on the membranes of various cells in the body, such as parathyroid and kidney cells (Nature 366:574, 1993; J. Bone Miner. Res. 9, Supple. 1, s282, 1994; J. Bone Miner. Res. 9, Supple. 1, s409, 1994; Endocrinology 136:5202, 1995), are important to the regulation of the extracellular calcium ion concentration. For example, concentration of extracellular calcium ion regulates the bone resorption by osteoclasts (Bioscience Reports 10:493, 1990), secretion of parathyroid hormone (PTH) from parathyroid cells and secretion of calcitonin from C-cells (Cell Calcium 11:323, 1990). Parathyroid cells thus have at their surface the calcium sensing receptor (CaSR), which detects changes in extracellular calcium concentration and initiates the functional response of this cell, which is a modulation of the secretion of the parathyroid hormone (PTH). Secretion of PTH increases extracellular calcium ion concentration by acting on various cells, such as bone and kidney cells, and the extracellular calcium ion concentration reciprocally inhibits the secretion of PTH by acting on parathyroid cells. The reciprocal relationship between calcium concentration and PTH level is an essential mechanism for calcium homeostasis maintenance.
The cloning of the calcium receptor by Brown in 1993 consequently demonstrated two possible signalling pathways for this G protein coupled receptor: one pathway by activation of the Gi protein (sensitive to the pertussis toxin) which stimulates phospholipase C and inhibits adenylate cyclase; the other pathway by activating the Gq protein responsible for mobilising intracellular calcium. These two signalling pathways, either independently of one another or together, can be activated so as to trigger the associated biological effect. On its extracellular portion, the calcium receptor is a low affinity receptor which is stimulated by millimolar concentrations of agonists, in particular the calcium ion Ca2+. In addition, this receptor can also be activated by some divalent metals (magnesium) or trivalent metals (gadolinium, lanthanum, etc.) or else by polycationic compounds such as neomycin or spermine.
Several classes of calcimimetic compounds have been disclosed for regulating extracellular calcium ion concentration, particularly for reducing or inhibiting secretion of PTH. For example, U.S. Pat. Nos. 6,011,068 and 5,981,599 disclose arylalkylamines that are calcium receptor active molecules. EP 933354; WO 0021910, WO 96/12697; WO 95/11221; WO 94/18959; WO 93/04373; WO 06/123725, AU 2004202208, Endocrinology 128:3047, 1991; Biochem. Biophys. Res. Commun. 167:807, 1990; J. Bone Miner. Res. 5:581, 1990; and Nemeth et al., “Calcium-binding Proteins in Health and Disease,” Academic Press, Inc., pp. 33-35 (1987) disclose various agents that interact with calcium receptors.
Dauban et al., Bioorg. Med. Chem. Let. 10:2001-4, 2000, disclose various N1-arylsulfonyl-N2-(1-aryl)ethyl-3-phenylpropane-1,2-diamine compounds as calcimimetics acting on the calcium sensing receptor.
Oikawa et al., in U.S. Pat. No. 6,403,832, and publication No. US2002/143212, describes aryl amine compounds useful as chiral intermediates in the synthesis of optically active propionic acid derivatives. Chassot et al., U.S. Pat. No. 6,436,152, describes arylalkylamine compounds useful as hair dye precursor compounds. Other calcimimetic compounds are disclosed in U.S. Pat. Nos. 6,313,146; 6,001,884; PCT publications WO 01/34562; WO 01/90069; WO 02/059102; WO 02/12181; WO 05/115975; WO 06/117211; WO 06/123725; WO 08/059,854; WO 08/019,690; WO 08/057,282.